AWWA WQTC71446

This powerpoint presentation begins by providing a brief overview of surface circulators installed in Occoquan Reservoir in 2006 to improve dissolved oxygen conditions/control manganese concentrations. Research objectives included the following: analyze the effects of surface circulator operation on thermal stratification and dissolved oxygen distribution; model the influence of surface circulators in Occoquan Reservoir; and, evaluate the limits of surface circulators for improving dissolved oxygen concentrations in lakes/reservoirs. Experimental methods include: vertical profiling; transects from NW to WB; near-field profiling; sample collection; and, ADV profiling of the near-field. Topics presented include: modeling of Occoquan Reservoir; representation of the circulators; constituent interaction; calibrating W2 and circulation flow rate; and, virtual lake simulation. Presentation summary includes the following: the surface circulation system was undersized for adequately oxygenating Occoquan Reservoir; the surface circulation system should have the intake near the sediments at the deepest part of the reservoir for the highest efficiency; the sediments' anoxic fraction is best influenced when the flow rate produces a turn over period close to 20 days; the water temperature is easily influenced by circulation and behaves predictably like a conservative constituent; and, the dissolved oxygen is harder to influence, and its vertical distribution is a function of supply and demand within the water column. Includes figures.